1. Field of the Invention
This invention relates to methods and apparatus for erecting tray-type cartons, more particularly for erecting from a blank of foldable sheet material a rectangular tray-type carton of the kind having a base formed from a base panel of the blank, a side wall upstanding from the base and formed from four side wall panels, gusset folds secured against the side wall at the corners of the carton and formed from gusset panels by which the side wall panels are joined integrally together, and a continuous peripheral flange outturned from the side wall around the mouth of the carton, the flange being formed from elongate panels carried by the side wall panels and formed at their ends with tabs which are secured together in overlapping relation at the corners of the carton. A flat closure lid can be attached to the carton, for example by heat-sealing the margin of the lid to the upper surface of the peripheral flange.
2. Description of the Prior Art
In the erection of rectangular tray-type cartons having peripheral flanges from flat blanks, it is known to form the flanges by the same operation as is used to fold up the side wall panels of the cartons in relation to the carton bases. Such a method, however, has several disadvantages attendant upon the formation of the peripheral flanges. It is also known from our copending British Patent Application No. 8213491 (Publication No. 2120161), as a first step in the folding process, to fold up from the plane of the blank those of the tabs which are to be uppermost in the erected carton, so that they will not interfere with the other tabs but will be correctly positioned during the subsequent steps of the folding process. In the process described in our said application, the subsequent steps comprise: (a) at a first station, forming the side wall by folding up the side wall panels in relation to the base panel whilst folding the gusset panels to form the gusset folds, such folding being accompanied by movement of the elongate panels with the side wall panels as coplanar extensions thereof with the exception of the said uppermost ones of the tabs,
(b) moving the partially erected carton from the first station to a second station,
(c) at the second station, folding the elongate panels outwardly in relation to the side wall and into generally coplanar relation with one another, with the said uppermost tabs overlying other ones of the tabs at the corners of the carton, and
(d) securing the overlapping tabs together at the corners of the carton to form a continuous peripheral flange.
In the preferred embodiment the folding is effected by a punch and die arrangement. This process has proved commercially successful but it does in practice require the use of a number of separate operating stations and an indexing conveyor to stop the movement of the cartons at the second station for folding of the two pairs of opposed elongate panels.